DevTools: make debugger's rawLocationToUILocation return nullable type

third_party/WebKit/Source/devtools/front_end/timeline/TimelineUIUtils.js

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  * Copyright (C) 2012 Intel Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 588 matching lines @@
      * @return {?string}
      */
     function linkifyLocationAsText(scriptId, lineNumber, columnNumber) {
       var debuggerModel = target ? target.model(SDK.DebuggerModel) : null;
       if (!target || target.isDisposed() || !scriptId || !debuggerModel)
         return null;
       var rawLocation = debuggerModel.createRawLocationByScriptId(scriptId, lineNumber, columnNumber);
       if (!rawLocation)
         return null;
       var uiLocation = Bindings.debuggerWorkspaceBinding.rawLocationToUILocation(rawLocation);
-      return uiLocation.linkText();
+      return uiLocation ? uiLocation.linkText() : null;
     }
 
     /**
      * @return {?string}
      */
     function linkifyTopCallFrameAsText() {
       var frame = TimelineModel.TimelineData.forEvent(event).topFrame();
       if (!frame)
         return null;
       var text = linkifyLocationAsText(frame.scriptId, frame.lineNumber, frame.columnNumber);
@@ skipping 1688 matching lines @@
    * @param {string=} warningType
    */
   appendWarningRow(event, warningType) {
     var warning = Timeline.TimelineUIUtils.eventWarning(event, warningType);
     if (warning)
       this.appendElementRow(Common.UIString('Warning'), warning, true);
   }
 };
 
 Timeline.TimelineUIUtils._categoryBreakdownCacheSymbol = Symbol('categoryBreakdownCache');